1. Field of the Invention
The present invention generally relates to a sensor and actuating mechanism used to inflate a vehicle occupant restraint system and more particularly to an actuating mechanism which utilizes the inertial force of a non-uniform mass to break a frangible actuating member.
2. Prior Art
Substantially all vehicles currently being marketed include a vehicle occupant restraint *system in the form of one or more inflatable air bags. In all forms of this type of occupant restraint system, a source of pressurized gas is confined within a fixed chamber. Upon sensing a collision having a pre-determined magnitude, the confined gas is released to fluidly fill the inflatable air bags. The inflated air bag will reduce the impact to which the occupants are subjected thereby providing a substantial margin of safety for vehicle occupants.
The prior art discloses a number of mechanical devices used to detect the forces generated by a vehicle collision. Upon sensing a force of predetermined magnitude, this device actuate means for inflating the vehicle occupant restraint system. In one of the mechanisms disclosed by the prior art, a shaft is used to support a frangible metal element, the shaft being held in place by a complex link mechanism. The link mechanism consists of a plurality of coupled projections which are oriented with respect to each other at predetermined, fixed angles. When the integrity of the link mechanism is maintained, the shaft will be held in place and the source of pressurized gas unable to break the frangible metal element. The structure of this sensing and actuating mechanism is inadequate. In order to provide the ability to respond to a collision which imposes a force from any direction, the integrity of the link mechanism depends upon the precise orientation of the coupled projections. The substantial difficulties which are encountered in predicting the direction of a collision force for the purpose of angularly orienting the link mechanism renders the device inadequate for its purpose.
Another category of sensing and actuating mechanisms taught by the prior art utilizes a resiliently biased lever arm which is maintained in its quiescent position through the use of a spherical weight. The spherical weight is located within a bore, the position being maintained by a compression spring. When the inertia of a collision displaces the spherical weight, the resiliently biased lever arm will engage a pin which will be urged against and fragmentize a gas cylinder. When the cylinder is fractured, the source of pressurized gas will be permitted to inflate the occupant restraint system. A problem inherent in this device is its inability to react to an inertial force which will not displace the spherical ball from its initial position (e.g., a force substantially aligned with the compression spring and bore). Since an objective of all passive restraint systems is to provide the ability to react to a collision irrespective of the direction in which the impact occurs, this device is inadequate for its intended purpose.
The present invention substantially overcomes the inadequacies of the devices taught by the prior art. In the present invention, a frangible sensor shaft supports an actuator piston which is used as a valve between a source of pressurized gas and one or more inflatable air bags. A sensing member comprises a sensor weight of non-uniform mass which is secured about the exterior surface of the sensor shaft. The non-uniform mass of the sensor weight will be responsive to inertial forces from any direction. Upon detecting an inertial force of a predetermined magnitude, the sensor weight will impose a lateral shearing force against the surface of the sensor shaft which is sufficient to fragmentize the shaft. When the supporting sensor shaft is fragmentized, the actuator piston will be displaced thereby opening a conduit intermediate the source of pressurized gas and the inflatable air bags.